The present invention concerns a selective process for the manufacture of glycol monoethers and more particularly the monoethers of monoethyleneglycol.
Presently, the manufacture of these products takes place in known manner, by reaction between an alcohol and ethylene oxide, in the liquid phase, in the presence of a catalyst. In this type of procedure, the monoether of the monoethyleneglycol formed has the same reactivity with respect to the ethylene oxide as does the initial alcohol, and reacts, as soon as it has been formed, competitively with the alcohol, with ethylene oxide in order to yield the monoether of diethyleneglycol which, in its turn leads to the formation of the monoether of the oligoethyleneglycols following a statistical distribution. Furthermore, the proportion of these derivatives of oligoethyleneglycol increases considerably with the molecular weight of the alcohol being used, so that it is impossible industrially to ensure a manufacture of the monoethers of monoethyleneglycol derived from alcohols comprising more than two carbon atoms without formation of considerable amounts of by-products.
The hydrogenolysis (destructive hydrogenation) of open acetals leads to the simultaneous and equimolecular formation of ether and of alcohol according to the reaction: ##STR1##
This reaction has been known since the work of CABANAC --Reports of the French Academy of Sciences--1929--first semester--Vol. 188--No. 19, page 1251. French Patent No. 2,422,614 describes an improved procedure for the hydrogenolysis of acetals and of ketals of organic hydrocarbons, by operating in the presence of a catalyst composed of a halide of an element of Group III A of the Periodic Table, such as AlCl.sub.4, BF.sub.3, etc. and of a hydrogenation catalyst constituted solely of platinum or of rhodium having been deposited on a support, in the liquid phase, at a temperature between -15.degree. and +125.degree. C., and under a pressure between 3.5 and 140 atmospheres.